Class 11 Physics Kinetic Theory Specific Heat of Diatomic gases (rigid)

Specific Heat of Diatomic gases (rigid)

  • A rigid diatomic gas means they will have translational as well as rotational degree of freedom but not vibrational.
  • They are rigid oscillator.
  • A rigid diatomic molecule will have 3 translational degrees of freedom and 2 rotational degrees of freedom. Total 5 degrees of freedom.
  • By law of equipartition of energy, each degree of freedom will contribute (1/2) kB
  • Therefore 5 degree of freedom will contribute (5/2) kB
  • Therefore the total internal energy of 1 mole of gas, U=(5/2) kBTxNA=(5/2)RT
  • Specific heat capacity at constant volume(CV) =dU/dT=(5/2)R
  • Specific heat capacity at constant pressure of a rigid diatomic is given as CP=(7/2)R
  • Ratio of specific heats γ=CP/CV=(7/5)

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